1. Field of the Invention
The present invention relates to an engine management system and more particularly relates to a system for controlling delivery of fuel to an internal combustion engine such as an aircraft engine which system has a primary control unit and a secondary control unit. Switching from the primary control unit to the secondary control unit occurs under certain predetermined operational conditions.
2. Background of the Invention
Redundant engine management systems for internal combustion engines are well known. For example, aircraft engines conventionally have back-up electrical and fuel systems in the event of a failure. The following patents are representative of prior art systems in this area.
U.S. Pat. No. 4,577,605 discloses an arrangement for controlling fuel metering to an internal combustion engine which is equipped with a microprocessor and an emergency control system. In the event of a microprocessor failure due to a defect, the system attempts to restart the microprocessor. At the same time, an emergency operation pulse generator assumes control of the fuel metering apparatus. The emergency control system is stated to be particularly suited for fuel metering apparatus which serve to control internal combustion (IC) engines for motor vehicles.
U.S. Pat. No. 5,233,964 shows an auxiliary control for reducing the processing load of an engine computer by directly controlling a fuel injection system of an IC engine. When the computer is unable to provide updated delay times and pulse with time periods, the auxiliary controller maintains limited engine operation in the event of a failure of the engine control computer. A delay time and a pulse width time period are continuously calculated by the engine controller and are provided to the auxiliary controller. The most recently-received delay time and pulse width time period are then used by the auxiliary controller to control up to eight identified fuel injectors. By initializing the auxiliary controller each time it is used, the auxiliary controller can be made universal in that one controller design can be used to interchangeably service a variety of engines.
U.S. Pat. No. 4,750,463 discloses an electronically regulated fuel injection system for an internal combustion engine with a switchable safety and emergency driving device which mechanically couples the accelerator pedal to the regulator. The coupling operatively interferes with the mechanical connection between a controller and a final control element that determines the quantity of fuel to be injected after a false signal has been output by a signal processing unit to a switchover element which switches over control of the final control element to the simple regulator.
U.S. Pat. No. 4,748,566 relates to an engine control apparatus for internal combustion engines which engine control has two computing means, one for main engine control signals and the other redundantly provided for auxiliary engine control signals. Switching from the main to the auxiliary engine control signals occurs when the computing means for the main engine control signal is not properly operating. When the number of changes of state in the output of the main computer monitor exceeds a predetermined value, the malfunction of the main computer is determined to be serious so that the back up computer provides a switching request signal. Under the condition of the existence of the switching request signal and confirmation that the back up computer is properly operating, switching from the main to the back up computer takes place.
While the foregoing engine control systems are, in many cases effective, they are often complicated or are adapted-only to specific engine arrangements. Accordingly, there exists a need for a simple, yet effective, engine control and management system which will switch power from one control to another under certain predetermined conditions.
Accordingly, it is a primary object of the present invention to provide an engine management system for internal combustion engines which has a primary and a secondary control unit which each sense selected parameters to make control adjustments. Switching to the secondary control unit occurs when a power switching unit is triggered by the presence or loss of specific output signal from the primary control unit.
It is another object of the present invention to provide an engine management system applicable to internal combustion engines of various types which system is simple and which relies upon a specific output signal from the primary system to initiate switching.
Another object of the present invention is to provide an engine management and control system which will, upon the occurrence of certain events, switch to a secondary control system capable of controlling engine operation based on sensed parameters instead of relying upon selected default values.
It is another object of the present invention to provide an engine management control system which can be operated to control any selected number of fuel injectors and which can redirect the output of the power supply circuit based on any number of selected operating conditions.
It is another object of the present invention to provide a primary engine control unit which may be configured to receive information from and send instructions to one or two ignition systems.